JP2022141038A - flow detector - Google Patents

Abstract

To provide a flow detector that can reduce the influence of an external force and vibration on a channel and highly accurately detect a change in shape of the channel in association with a change in pressure of fluid.SOLUTION: A flow detector 1 comprises: a channel 10 that has a flow wall 11 swelling and contracting according to a change in pressure of fluid flowing inside the channel; a pressure receiving part 20 that has an inner layer part 21 covering at least part of the periphery of the flow wall 11 and changing its volume according to the swelling and contracting of the flow wall 11 and a non-air permeable outer layer part 22 surrounding the inner layer part 21, and is provided, in the outer layer part 22, with a window part 23 through which gas inside the inner layer part 21 comes in and goes out in association with the change in volume of the inner layer part 21; and a pressure detection part 30 that has a cantilever 32 bent and deformed by the gas coming in and going out through the window part 23.SELECTED DRAWING: Figure 7

Description

The present disclosure relates to flow detection devices.

Patent Literature 1 listed below discloses a flow rate abnormality detection device that detects a flow rate abnormality without contact with a fluid. In this flow rate anomaly detection device, a flexible tube connected to a roller pump is sandwiched between a case body and a lid connected by a hinge. A strain gauge is provided in the case main body, and by pressing the strain gauge against the outer surface of the tube, the pressure received from the tube is measured to detect flow rate abnormality.

JP 2018-132364 A

By the way, when detecting a flow state of a very small flow rate, the displacement of the tube is very small, for example, 1 μm or less. As in the above conventional technology, in a sensor that measures the displacement by pressing a strain gauge or the like against the tube, the signal level becomes small, and the influence of the displacement due to the external force and vibration from the outside becomes relatively large. Then, this becomes a noise source, and there is a possibility that the displacement of the tube cannot be detected accurately. In other words, even if the sensor itself has high performance and high resolution, there is a problem that the S/N ratio deteriorates due to disturbance, making measurement difficult.

The present disclosure has been made in view of the above problems, and provides a flow detection device that can reduce the influence of external force, vibration, etc. on the flow path and can detect the shape change of the flow path due to the pressure change of the fluid with high accuracy. for the purpose of providing

(1) A flow detection device according to an aspect of the present disclosure includes a flow path having a flow wall that expands and contracts due to changes in the pressure of a fluid flowing inside, and at least a portion of the flow wall that covers at least a portion of the flow wall. It has an inner layer part whose volume changes according to expansion and contraction, and an impermeable outer layer part surrounding the inner layer part, and a window through which gas in the inner layer part enters and exits according to the volume change of the inner layer part in the outer layer part. and a pressure detecting portion having a cantilever that is flexurally deformed by the gas flowing in and out of the window.

According to the flow detection device according to this aspect, when the flow wall of the flow path expands and contracts due to a change in the pressure of the fluid flowing inside, the volume of the inner layer of the pressure-receiving section covering at least a part of the periphery of the flow wall fluctuates, Gas enters and exits through windows provided in the air-impermeable outer layer covering the inner layer. Then, the cantilever is bent and deformed by the gas entering and exiting through the window. Even if the amount of gas flowing in and out of the window is very small, the cantilever is flexibly deformed in response to the pressure of the gas with high sensitivity. Therefore, the flow state of the fluid can be detected with high sensitivity.
On the other hand, when the channel receives an external force from the outside or vibrates, the flow wall does not swell or contract, so the volume of the inner layer of the pressure-receiving portion does not change, and the cantilever hardly reacts.
Therefore, according to the flow detection device according to this aspect, it is possible to reduce the influence of external force, vibration, and the like on the flow path, and to detect the shape change of the flow path due to the pressure change of the fluid with high accuracy.

(2) In the flow detection device of aspect (1), the inner layer portion may be formed of an elastic body having communicating cells.

In this case, the inner layer portion can elastically support the flow wall of the channel. Further, when the flow wall expands and contracts, the inner layer portion can be elastically deformed according to the expansion and contraction. Furthermore, the elastic deformation of the inner layer can dampen the vibration of the flow path.

(3) In the flow detection device of aspect (2), the elastic body may be polyurethane foam.

In this case, the inner layer portion of the pressure receiving portion can be produced at low cost.

(4) In the flow detection device according to any one of aspects (1) to (3), the inner layer portion may be softer than the flow wall.

In this case, for example, when the flow wall expands, the inner layer, which is softer than the flow wall, begins to collapse before the flow wall completely collapses in the thickness direction due to the internal pressure of the fluid. It is possible to detect the change in the shape of the flow path with high sensitivity due to the change in pressure of the fluid.

(5) In the flow detection device according to any one of aspects (1) to (4), the pressure detection unit includes a cavity housing that forms a differential pressure chamber that communicates with the window with the cantilever interposed therebetween. good too.

In this case, since the cantilever is less likely to be affected by the outside air, it is possible to detect the change in the shape of the flow path due to the pressure change of the fluid with high accuracy.

(6) The flow detection device according to any one of aspects (1) to (5) may include a pressing member that presses the pressure receiving portion against the flow wall.

In this case, since the inner layer of the pressure-receiving part is in close contact with the flow wall, the responsiveness to volume fluctuations of the inner layer due to expansion and contraction of the flow wall is improved, and the shape change of the flow path due to changes in fluid pressure is sensitive. can be detected well.

(7) In the flow detection device according to any one of aspects (1) to (6), the pressure receiving portion includes a tubular portion surrounding the flow wall, and the tubular portion extends in the longitudinal direction of the flow path. A slit may be formed extending to the

In this case, the flow path can be inserted into the pressure receiving portion through the slit, which facilitates installation of the pressure receiving portion on the flow wall.

(8) In the flow detection device according to any one of aspects (1) to (7), the flow wall may be surrounded by a plurality of flow detection units including the pressure receiving section and the pressure detecting section. .

In this case, since the flow wall is surrounded by a plurality of flow detection units, the volume of the inner layer of the pressure receiving portion per one flow detection unit can be reduced. As a result, the responsiveness of volume fluctuations of the inner layer due to expansion and contraction of the flow wall is improved, and changes in the shape of the flow path due to pressure changes of the fluid can be detected with high sensitivity.

(9) In the flow detection device of aspect (8), the plurality of flow detection units includes a first flow detection unit and a second flow detection unit arranged opposite to each other with the flow path interposed therebetween, A signal processing circuit may be provided that adds the signals output from the detection unit and the pressure detection section of the second flow detection unit to cancel the vibration noise of the flow path.

In this case, as a result of dividing into a plurality of flow detection units, even if vibration noise of the flow path is picked up, the first flow detection unit and the second flow detection unit arranged opposite to each other across the flow path By adding the signals output from the pressure detection section of the unit, it is possible to cancel the vibration noise of the flow path and detect the shape change of the flow path due to the pressure change of the fluid with high accuracy.

According to the above-described aspect of the present disclosure, it is possible to provide a flow detection device that reduces the influence of external force, vibration, and the like on the flow path and that can detect the shape change of the flow path due to the pressure change of the fluid with high accuracy.

1 is a cross-sectional configuration diagram of a flow detection device according to a first embodiment; FIG. 2 is a cross-sectional view taken along line II-II shown in FIG. 1; FIG. 2 is a plan view showing a configuration example of a cantilever according to the first embodiment; FIG. 3 is a circuit diagram showing a configuration example of an analog circuit section according to the first embodiment; FIG. FIG. 5 is a diagram showing a state in which the flow path is displaced upward with respect to the pressure receiving portion due to an external force, vibration, or the like in the flow detection device according to the first embodiment; FIG. 5 is a diagram showing how the flow path is displaced to the right with respect to the pressure receiving portion due to an external force, vibration, or the like in the flow detection device according to the first embodiment; FIG. 5 is a diagram showing how the flow wall of the flow path swells due to the pressure change of the fluid flowing therein in the flow detection device according to the first embodiment. FIG. 5 is a diagram showing how the flow wall of the flow channel shrinks due to the pressure change of the fluid flowing inside in the flow detection device according to the first embodiment. It is a figure which shows an example of the output waveform data of the flow detection apparatus which concerns on 1st Embodiment. It is a cross-sectional block diagram of the flow detection apparatus which concerns on 2nd Embodiment. It is a cross-sectional block diagram of the flow detection apparatus which concerns on 3rd Embodiment. It is a cross-sectional block diagram of the flow detection apparatus which concerns on 4th Embodiment. It is a block diagram which shows the 1st example of the signal-processing circuit based on 4th Embodiment. FIG. 12 is a configuration diagram showing a second example of a signal processing circuit according to the fourth embodiment;

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional configuration diagram of a flow detection device 1 according to the first embodiment. FIG. 2 is a cross-sectional view taken along line II-II shown in FIG.
The flow detection device 1 includes a flow path 10, a pressure receiving section 20, and a pressure detection section 30, as shown in FIG.

The channel 10 has a flow wall 11 that expands and contracts according to changes in the pressure of the fluid flowing inside. The channel 10 of the present embodiment is a so-called liquid-sending tube having at least flexibility and elasticity, and is elongated with a constant inner diameter (cross-sectional area). In addition, depending on the type of fluid, application, etc., the flow wall 11 may be subjected to various treatments such as oxidation treatment as necessary, or may be given various properties such as heat resistance and transparency. .

The flow path 10 is connected to, for example, a pulsation pump (not shown). The pulsation pump can be exemplified by a so-called roller pump that sucks fluid stored in a water supply tank and discharges the fluid while pulsating it at a known reference frequency. Since the channel 10 has at least flexibility and elasticity, the flow wall 11 undulates and contracts according to the pulsation of the fluid.

The pressure-receiving portion 20 includes an inner layer portion 21 that covers at least a portion (entire circumference in the first embodiment) of the periphery of the flow wall 11 and that varies in volume according to expansion and contraction of the flow wall 11, and a non-ventilating portion that covers the inner layer portion 21. and a flexible outer layer 22 . The outer layer portion 22 is provided with a window portion 23 through which the air (gas) inside the inner layer portion 21 enters and exits as the volume of the inner layer portion 21 changes. When the pressure detection unit 30 has the cavity housing 35 and can form an airtight space as in the present embodiment, the inner layer 21 is filled with a gas other than air (for example, nitrogen gas). I don't mind.

The inner layer portion 21 and the outer layer portion 22 form a cylindrical portion 20A concentric with the central axis O of the flow path 10 . The inner layer portion 21 is formed of an elastic body having communicating cells. Polyurethane foam can be exemplified as the elastic body forming the inner layer portion 21 . The inner layer portion 21 only needs to be elastically deformable according to the internal pressure of the fluid, and it is particularly preferable that the inner layer portion 21 is softer than the flow wall 11 because the responsiveness to volume fluctuations increases.

The inner layer portion 21 may be a space (hollow), or may be a fiber cushion or the like capable of retaining air between fibers, as long as the volume can be varied according to the expansion and contraction of the flow wall 11 . Alternatively, the inner layer portion 21 may be made of open cells by crushing closed cells such as rubber sponge with a roller or the like.

The outer layer portion 22 covers the entire outer surface of the inner layer portion 21 except for the window portion 23 . Specifically, as shown in FIG. 2, the outer layer portion 22 covers the outer peripheral surface of the inner layer portion 21 and both end surfaces of the inner layer portion 21 in the longitudinal direction. The window portion 23 is formed at an intermediate position in the longitudinal direction of the outer peripheral surface of the outer layer portion 22 .

The outer layer portion 22 is, for example, a skin layer (surface layer) such as integral skin foam or coated urethane in which the inner layer portion 21 is soft, and is harder than the inner layer portion 21 and has almost no air permeability. It should be noted that the outer layer portion 22 may be made of hard plastic, metal, or the like as long as it has air permeability and can maintain the outer shape of the pressure receiving portion 20 . The term “impermeable” as used herein does not necessarily mean that the air is completely impermeable.

Returning to FIG. 1 , the window portion 23 is formed in part of the outer peripheral surface of the outer layer portion 22 . Through the window portion 23, the surface of the inner layer portion 21, that is, the communicating cells are exposed. A holding member 24 that holds the cylindrical portion 20</b>A including the inner layer portion 21 and the outer layer portion 22 is provided around the window portion 23 . The holding member 24 airtightly surrounds the window portion 23 and is connected to the sensor substrate 31 of the pressure detection portion 30 .

The pressure detection section 30 includes a sensor substrate 31 , a cantilever 32 , an analog circuit section 33 , a digital processing section 34 and a cavity housing 35 .
The sensor board 31 is, for example, a printed circuit board. A through-hole 31a is formed through the sensor substrate 31 in the thickness direction. The through hole 31 a is arranged inside the holding member 24 and communicates with the window portion 23 .

The cavity housing 35 is formed in a cylindrical shape with a bottom, and is connected to the surface of the sensor substrate 31 opposite to the surface to which the holding member 24 is connected so as to surround the through hole 31a. The cantilever 32 is arranged inside the cavity housing 35 . Inside the cavity housing 35, the cantilever 32 is attached to the open end of a cylindrical lever support 36 connected to surround the through hole 31a.

The cavity housing 35 is divided into a first air chamber 30A and a second air chamber 30B with the cantilever 32 interposed therebetween. The first air chamber 30</b>A and the second air chamber 30</b>B communicate with each other through a communication hole 42 provided in the cantilever 32 . The window portion 23 of the pressure receiving portion 20 and the through hole 31a of the sensor substrate 31 communicate with the second air chamber 30B. The first air chamber 30A is a differential pressure chamber (airtight chamber) communicating with the second air chamber 30B with the cantilever 32 interposed therebetween.

FIG. 3 is a plan view showing a configuration example of the cantilever 32 according to the first embodiment.
The cantilever 32 is formed on a semiconductor substrate 40 such as an SOI substrate, for example. A gap G1 and a gap G2 are provided in the semiconductor substrate 40, and a lever main body 41 and a lever support portion 43 of the cantilever 32 are formed. The gap G1 and the gap G2 serve as communication holes 42 that communicate the first air chamber 30A and the second air chamber 30B.

The base end portion 41b of the lever main body 41 is connected to the lever support portion 43 so as to be cantilevered, and the distal end portion 41a thereof is a free end. The lever main body 41 has a plate shape extending in one direction from the base end portion 41b toward the tip end portion 41a, and is flexurally deformed according to the pressure difference between the first air chamber 30A and the second air chamber 30B of the cavity housing 35. do.

The gap G1 is a U-shaped (C-shaped) groove formed between the semiconductor substrate 40 and the outer peripheral edge of the lever body 41 and penetrating the semiconductor substrate 40 in the thickness direction. The gap G2 is a U-shaped (C-shaped) groove formed in the base end portion 41b of the lever body 41 and penetrating the lever body 41 in the thickness direction. The gap G<b>2 is arranged at the center of the lever body 41 in the width direction at the base end 41 b of the lever body 41 .

Two lever support portions 43 are arranged side by side in the width direction of the lever body 41 across a gap G2, connect the lever body 41 and the semiconductor substrate 40, and support the lever body 41 in a cantilever state. . The support widths of the two lever support portions 43 in the width direction of the lever main body 41 are made equal. Therefore, when the lever main body 41 is flexurally deformed, the stress per unit area acting on one lever support portion 43 is equal to the stress per unit area acting on the other lever support portion 43 .

A doped layer 44 (impurity semiconductor layer), which is a piezoresistor (resistive element), is formed on the semiconductor substrate 40 so as to include the lever body 41 . The doped layer 44 is formed by doping a dopant (impurity) such as phosphorus by various methods such as ion implantation and diffusion. A portion of the doped layer 44 where the lever main body 41 is formed (including the portion formed on the lever support portion 43) functions as a resistor R1 (differential pressure detection resistor Rsen1).

The resistance value of the resistor R1 changes according to the deflection amount of the lever support portion 43 . Although not shown, an electrode is formed on the upper surface of the doped layer 44 and made of a conductive material (for example, Au (gold) or the like) having an electrical resistivity lower than that of the doped layer 44 . This electrode functions as a first end and a second end of the resistor R1 (differential pressure detection resistor Rsen1).

Returning to FIG. 1, the analog circuit section 33 is a circuit that performs analog processing for detecting displacement according to bending deformation of the lever body 41 . This analog circuit section 33 is an AFE (analog front end). The analog circuit section 33 is arranged inside the cavity housing 35, that is, in the first air chamber 30A.

FIG. 4 is a circuit diagram showing a configuration example of the analog circuit section 33 according to the first embodiment.
As shown in FIG. 4 , the analog circuit section 33 includes a Wheatstone bridge circuit 61 and a differential amplifier circuit 62 . The Wheatstone bridge circuit 61 includes a resistor R1 (differential pressure detection resistor Rsen1) included in the cantilever 32, a resistor R2, a resistor R3, and a resistor R4.

The resistor R1 (differential pressure detection resistor Rsen1) has a first end connected to the reference voltage circuit Vref and a second end connected to the node N1. resistance changes. Resistor R1 is, for example, a piezoresistor (doped layer 44). The resistor R2 has a first end connected to the node N1 and a second end connected to the power supply GND.

The resistor R3 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N2. The resistor R4 has a first end connected to the node N2 and a second end connected to the power supply GND. The resistor R1 is configured within the cantilever 32, and the resistors R3 and R4 are external resistors provided outside the cantilever 32. FIG.

The resistor R2 (reference resistor Rref1) is, for example, a resistor formed to have the same temperature characteristics as the resistor R1, and may be configured within the cantilever 32 or may be provided outside near the cantilever 32. good too. By matching the temperature characteristics of the resistor R1 and the resistor R2, the analog circuit section 33 can reduce the influence of temperature fluctuations on the detection result.

The differential amplifier circuit 62 is, for example, a measurement amplifier (instrumentation amplifier), amplifies the potential difference between the node N1 and the node N2, and outputs it as an output signal. This potential difference becomes a value corresponding to the change in the resistance value of the piezoresistor, that is, a value based on the displacement of the cantilever 32 . The differential amplifier circuit 62 has an inverting input terminal (-terminal) connected to the node N1 and a non-inverting input terminal (+terminal) connected to the node N2.

Returning to FIG. 1, the digital processing unit 34 is, for example, a digital processing circuit such as a microcontroller, and converts the output waveform data corresponding to the differential pressure detected by the analog circuit unit 33 into pressure fluctuation information. The digital processing unit 34 is mounted (arranged) on, for example, the sensor substrate 31 and arranged outside the cavity housing 35 .

Next, the operation of the flow detection device 1 having the above configuration will be described with reference to FIGS. 5 to 9. FIG.

FIG. 5 is a diagram showing how the flow path 10 is displaced upward with respect to the pressure receiving portion 20 due to an external force, vibration, or the like in the flow detection device 1 according to the first embodiment.
As shown in FIG. 5, when the central axis O1 of the flow path 10 is displaced upward by a distance D1 with respect to the central axis O2 of the pressure receiving portion 20, the upper side of the inner layer portion 21 is elastically deformed and narrowed. Since the lower side of the portion 21 widens, the cross-sectional area of the inner layer portion 21 as a whole does not change. That is, since the volume of the inner layer portion 21 does not fluctuate, air does not flow in and out of the window portion 23, and the cantilever 32 hardly reacts.

FIG. 6 is a diagram showing how the flow path 10 is displaced to the right with respect to the pressure receiving portion 20 due to an external force, vibration, or the like in the flow detection device 1 according to the first embodiment.
As shown in FIG. 6, when the central axis O1 of the flow path 10 is displaced by a distance D2 to the right with respect to the central axis O2 of the pressure receiving portion 20, the right side of the inner layer portion 21 is elastically deformed and narrowed. Since the left side of the portion 21 widens, the cross-sectional area of the inner layer portion 21 as a whole does not change. That is, since the volume of the inner layer portion 21 does not fluctuate, air does not flow in and out of the window portion 23, and the cantilever 32 hardly reacts. The same applies when the flow path 10 is displaced in an oblique direction other than up, down, left, and right.

FIG. 7 is a diagram showing how the flow wall 11 of the flow path 10 swells due to the pressure change of the fluid flowing therein in the flow detection device 1 according to the first embodiment.
As shown in FIG. 7, when the flow wall 11 of the flow path 10 swells due to the pressure change of the fluid flowing inside, the inner layer portion 21 is compressed and its cross-sectional area becomes smaller. Then, the air in the communicating cells of the inner layer portion 21 is pushed out from the window portion 23, and the cantilever 32 is flexurally deformed.

That is, when the flow wall 11 of the flow path 10 expands and the inner layer portion 21 of the pressure receiving portion 20 is compressed and the cross-sectional area is reduced, air is pushed out from the window portion 23 and the pressure in the second air chamber 30B is increased. Become. Then, the cantilever 32 can detect the differential pressure between the first air chamber 30A and the second air chamber 30B, and can detect the shape change of the flow path 10 due to the increase in the internal pressure of the flow path 10. FIG.

FIG. 8 is a diagram showing how the flow wall 11 of the flow path 10 shrinks due to the pressure change of the fluid flowing therein in the flow detection device 1 according to the first embodiment.
As shown in FIG. 8, when the flow wall 11 of the flow channel 10 shrinks due to the pressure change of the fluid flowing inside (returns from the state shown in FIG. 7 to the original state), the inner layer portion 21 is restored and deformed. Its cross-sectional area returns to its original size. Then, air is taken into the inner layer portion 21 from the window portion 23, the differential pressure between the first air chamber 30A and the second air chamber 30B is relieved, and the cantilever 32 is restored and deformed to its original shape.

FIG. 9 is a diagram showing an example of output waveform data of the flow detection device 1 according to the first embodiment. In FIG. 9, the vertical axis is voltage [V] and the horizontal axis is time [sec].
As shown in FIG. 9, in the initial flow state in which the pulsating pump operates, the internal pressure of the flow path 10 changes due to the pulsating flow caused by the pulsating pump, and the flow wall 11 pulsates. Output waveform data of pressure change is obtained.

On the other hand, when clogging occurs in the flow path 10 on the downstream side of the flow detection device 1, the internal pressure of the flow path 10 rises immediately after the occurrence of clogging, and the pulsation output waveform data also increases. By looking at the magnitude of this output waveform data, it is possible to estimate the presence or absence of clogging in the channel 10 and the state of flow.

As shown in FIGS. 5 and 6 described above, the flow detection device 1 can eliminate noise due to external forces and vibrations, so that the SN ratio is improved, and the pressure change of the fluid due to the flow state (clogging, etc.) in the flow path 10 is suppressed. The accompanying shape change of the flow path 10 can be detected with high accuracy. Therefore, it is possible to accurately detect the flow state of a particularly small flow rate.

As described above, the flow detection device 1 according to the present embodiment includes the flow path 10 having the flow wall 11 that expands and contracts according to pressure changes of the fluid flowing inside, and at least a portion of the flow wall 11 that covers and flows. It has an inner layer portion 21 whose volume changes according to the expansion and contraction of the wall 11, and an air-impermeable outer layer portion 22 surrounding the inner layer portion 21. and a pressure detecting portion 30 having a cantilever 32 that is flexibly deformed by the air entering and exiting through the window portion 23 .

According to this flow detection device 1, when the flow wall 11 of the flow path 10 expands and contracts due to a change in the pressure of the fluid flowing inside, the inner layer portion 21 of the pressure receiving portion 20 covering at least a part of the periphery of the flow wall 11 expands. Air flows in and out through windows 23 provided in an air-impermeable outer layer 22 covering the inner layer 21 . The cantilever 32 is flexurally deformed by the air entering and exiting through the window 23 . Since the cantilever 32 flexibly deforms in response to the air pressure with high sensitivity even if the amount of air entering and exiting the window 23 is very small, the flow state of the fluid can be detected with high sensitivity.
On the other hand, when the channel 10 receives an external force from the outside or vibrates, the flow wall 11 does not expand or contract only by that force, so the inner layer portion 21 of the pressure receiving portion 20 does not change in volume, and the cantilever 32 hardly reacts. do not do.
Therefore, according to the flow detection device 1 according to this aspect, it is possible to reduce the influence of external forces, vibrations, and the like on the flow path 10 and detect the shape change of the flow path 10 due to the pressure change of the fluid with high accuracy.

In addition, in the flow detection device 1 of the present embodiment, the inner layer portion 21 is formed of an elastic body having communicating cells. According to this configuration, the inner layer portion 21 can elastically support the flow wall 11 of the channel 10 . Further, when the flow wall 11 expands and contracts, the inner layer portion 21 can be elastically deformed according to the expansion and contraction. Furthermore, the elastic deformation of the inner layer portion 21 can dampen the vibration of the flow path 10 .

Moreover, in the flow detection device 1 of the present embodiment, the elastic body is polyurethane foam. According to this configuration, the inner layer portion 21 of the pressure receiving portion 20 can be manufactured at low cost.

Moreover, in the flow detection device 1 of the present embodiment, the inner layer portion 21 is softer than the flow wall 11 . According to this configuration, for example, when the flow wall 11 expands as shown in FIG. starts to be crushed, the responsiveness to volume fluctuations of the inner layer portion 21 is improved, and the change in shape of the flow path 10 due to the pressure change of the fluid can be detected with high sensitivity.

In addition, in the flow detection device 1 of the present embodiment, as shown in FIG. 1, the pressure detection unit 30 is a cavity that forms a first air chamber 30A serving as a differential pressure chamber that communicates with the window 23 with the cantilever 32 interposed therebetween. A housing 35 is provided. According to this configuration, since the cantilever 32 is less likely to be affected by the outside air, it is possible to detect the shape change of the flow path 10 due to the pressure change of the fluid with high accuracy.

(Second embodiment)
Next, a second embodiment of the invention will be described. In the following description, the same reference numerals are given to the same or equivalent configurations as in the above-described embodiment, and the description thereof will be simplified or omitted.

FIG. 10 is a cross-sectional configuration diagram of the flow detection device 1 according to the second embodiment.
As shown in FIG. 10 , the flow detection device 1 of the second embodiment includes a pressing member 50 that presses the pressure receiving portion 20 against the flow wall 11 . The pressing member 50 has a pair of pressing pieces 51 .

The pressing piece 51 includes a fixed portion 51a, a movable portion 51b, a hinge 51c, and a fastened portion 51d. The fixed portion 51 a is fixed to the sensor substrate 31 outside the holding member 24 . The movable portion 51b is connected to the upper end portion of the fixed portion 51a via a hinge 51c. The movable portion 51 b has an arc shape with the same or substantially the same curvature as the outer peripheral surface of the pressure receiving portion 20 .

The fastened portion 51 d is provided at the upper end portion of the movable portion 51 b and is fastened to the fastened portion 51 d of the other pressing piece 51 via a bolt 52 and a nut 53 . The bolt 52 and the nut 53 can adjust the magnitude of the pressure applied by the pair of pressing pieces 51 to press the pressure receiving portion 20 .

According to the second embodiment having the above configuration, since the pressing member 50 that presses the pressure receiving portion 20 against the flow wall 11 is provided, the inner layer portion 21 of the pressure receiving portion 20 is in close contact with the flow wall 11 and the flow wall 11 expands. The responsiveness of the volume change of the inner layer portion 21 due to contraction is improved, and the shape change of the flow path 10 due to the pressure change of the fluid can be detected with high sensitivity.

Further, since the displacement of the outer shape of the pressure receiving portion 20 is suppressed by the pressing member 50 , it becomes easier to directly detect the shape change (expansion/contraction) of the flow path 10 due to the pressure change of the fluid in the inner layer portion 21 . Furthermore, since the tightening condition of the pressing member 50 can be optimized by the bolt 52 and the nut 53, variations in the inner diameter of the pressure receiving portion 20 can be absorbed. Furthermore, since the pressure receiving portion 20 is not exposed, noise caused by an external force acting directly on the pressure receiving portion 20 can be avoided.

(Third Embodiment)
Next, a third embodiment of the invention will be described. In the following description, the same reference numerals are given to the same or equivalent configurations as in the above-described embodiment, and the description thereof will be simplified or omitted.

FIG. 11 is a cross-sectional configuration diagram of the flow detection device 1 according to the third embodiment.
As shown in FIG. 11, in the pressure receiving portion 20 of the third embodiment, a slit 20B extending in the longitudinal direction of the flow channel 10 detachable from the flow wall 11 is formed in a cylindrical portion 20A surrounding the flow wall 11 . .

In other words, the cylindrical portion 20A of the pressure receiving portion 20 of the third embodiment is partially divided in the circumferential direction along the longitudinal direction of the flow path 10 from end to end. In addition, the inner wall surface of the slit 20B is covered with an air-impermeable outer layer portion 22 . The pressure receiving portion 20 of the third embodiment covers substantially the entire circumference of the flow wall 11 except for the slit 20B.

Moreover, in the third embodiment, a spacer 54 is sandwiched between the pair of pressing pieces 51 . The spacer 54 has, for example, a hole through which the bolt 52 can be inserted. By changing the thickness of the spacer 54, the magnitude of the pressure applied by the pressing member 50 to the pressure receiving portion 20 can be adjusted and fixed. there is

According to the third embodiment configured as described above, the pressure receiving portion 20 includes a cylindrical portion 20A surrounding the flow wall 11, and the cylindrical portion 20A extends in the longitudinal direction of the flow channel 10 that can be detached from the flow wall 11. Since the slit 20B is formed, installation of the pressure receiving portion 20 on the flow wall 11 is facilitated. That is, since the pressure-receiving portion 20 is split, the pressure-receiving portion 20 can be attached so as to cover the flow wall 11 . That is, the trouble of attaching the pressure receiving part 20 from the end of the flow path 10 is eliminated.

Further, in the third embodiment, since the spacer 54 is sandwiched between the pair of pressing pieces 51, it becomes easy to adjust the magnitude of the pressure applied to the pressure receiving portion 20 by the pressing member 50. FIG.

(Fourth embodiment)
Next, a fourth embodiment of the invention will be described. In the following description, the same reference numerals are given to the same or equivalent configurations as in the above-described embodiment, and the description thereof will be simplified or omitted.

FIG. 12 is a cross-sectional configuration diagram of the flow detection device 1 according to the fourth embodiment.
As shown in FIG. 12 , the flow detection device 1 of the fourth embodiment includes a plurality of flow detection units 2 including a pressure receiving section 20 and a pressure detection section 30 , and the plurality of flow detection units 2 detect the flow around the flow wall 11 . surrounds the Although the flow detection device 1 has two flow detection units 2 in the example shown in FIG. 12 , it may have three or more flow detection units 2 .

The flow detection device 1 includes a first flow detection unit 2A and a second flow detection unit 2B arranged opposite to each other with a flow path 10 interposed therebetween. The first flow detection unit 2A and the second flow detection unit 2B each include a semicircular pressure receiving portion 20, a pressure detecting portion 30, and a coupling 55 that constitutes the pressing member 50 described above.

The semicircular pressure-receiving portions 20 are arranged to face each other across the flow path 10 and cover at least a portion (substantially the entire circumference in the fourth embodiment) of the flow wall 11 . The coupling 55 has a semicircular arc shape with the same or substantially the same curvature as the outer peripheral surface of the pressure receiving portion 20 . A coupling 55 between the first flow detection unit 2A and the second flow detection unit 2B is fastened via a bolt 52 and a nut 53 with a spacer 54 interposed therebetween, so that the magnitude of pressure pressing the pressure receiving portion 20 can be adjusted. It's becoming

The flow detection device 1 includes a signal processing circuit 70 that processes signals output from the pressure detection sections 30 of the first flow detection unit 2A and the second flow detection unit 2B.

FIG. 13 is a configuration diagram showing a first example of the signal processing circuit 70 according to the fourth embodiment.
As shown in FIG. 13, the resistance R1 of the cantilever 32 of the first flow detection unit 2A and the resistance R4 of the cantilever 32 of the second flow detection unit 2B may be incorporated into the same Wheatstone bridge circuit 61.

The resistor R1 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N1. The resistor R1 is the variable piezoresistor (doped layer 44) of the cantilever 32 of the first flow sensing unit 2A. The resistor R2 has a first end connected to the node N1 and a second end connected to the power supply GND.

The resistor R3 has a first end connected to the reference voltage circuit Vref and a second end connected to the node N2. The resistor R4 has a first end connected to the node N2 and a second end connected to the power supply GND. Resistor R4 is a variable piezoresistor (doped layer 44) of cantilever 32 of second flow sensing unit 2B.

Differential amplifier circuit 62 amplifies the potential difference between nodes N1 and N2 and outputs it as an output signal. This potential difference becomes a value corresponding to the change in the resistance value of the piezoresistor, that is, a value based on the displacement of the cantilever 32 . The differential amplifier circuit 62 has an inverting input terminal (-terminal) connected to the node N1 and a non-inverting input terminal (+terminal) connected to the node N2.

FIG. 14 is a configuration diagram showing a second example of the signal processing circuit 70 according to the fourth embodiment.
Further, as shown in FIG. 14, signals output from the pressure detection units 30 of the first flow detection unit 2A and the second flow detection unit 2B are added by an adder circuit 71 to cancel the vibration noise of the flow path 10. good too.

In the example shown in FIG. 14, each of the first flow detection unit 2A and the second flow detection unit 2B includes a Wheatstone bridge circuit 61 and a differential amplifier circuit 62. The differential amplifier circuit 62 can adjust the gain so that the sensor sensitivities of the first flow detection unit 2A and the second flow detection unit 2B are the same. For example, when vibration noise of the flow path 10 is detected, the gain may be adjusted so that the vibration noise is minimized.

According to the fourth embodiment having the above configuration, as shown in FIG. 12 , the flow wall 11 is surrounded by a plurality of flow detection units 2 including the pressure receiving section 20 and the pressure detecting section 30 . By surrounding the flow wall 11 with a plurality of flow detecting units 2 in this manner, the volume of the inner layer portion 21 of the pressure receiving portion 20 per one flow detecting unit 2 can be reduced. As a result, the responsiveness of the volume change of the inner layer portion 21 due to the expansion and contraction of the flow wall 11 is improved, and the shape change of the flow channel 10 due to the pressure change of the fluid can be detected with high sensitivity.

In addition, the plurality of flow detection units 2 includes a first flow detection unit 2A and a second flow detection unit 2B arranged opposite to each other with the flow path 10 interposed therebetween, and as shown in FIG. A signal processing circuit 70 that adds the signals output from the pressure detection section 30 of the second flow detection unit 2B to cancel the vibration noise of the flow path 10 may be provided. According to this configuration, as a result of dividing into a plurality of flow detection units 2, even if vibration noise of the flow path 10 is picked up, the first flow detection unit 2A arranged oppositely with the flow path 10 interposed therebetween By adding the signals output from the pressure detection unit 30 of the second flow detection unit 2B, the vibration noise of the flow path 10 is canceled, and the shape change of the flow path 10 due to the pressure change of the fluid is detected with high accuracy. can.

While the preferred embodiments of the disclosure have been described and described, it is to be understood that they are exemplary of the disclosure and should not be considered limiting. Additions, omissions, substitutions, and other modifications may be made without departing from the scope of the disclosure. Accordingly, the present disclosure should not be considered limited by the foregoing description, but rather by the claims.

For example, in the above embodiment, the Wheatstone bridge circuit 61 is used to detect the change in the resistance value of the cantilever 32, but it is not limited to this case. Any configuration of the detection circuit may be used as long as it can detect the change in the resistance value of the cantilever 32 .
Further, in the above-described embodiment, the pressure detection unit 30 includes the cavity housing 35. However, for example, when the flow detection device 1 is arranged in a space that is hardly affected by outside air, the cavity housing 35 may be It doesn't matter if you don't.

Reference Signs List 1 Flow detection device 2 Flow detection unit 2A First flow detection unit 2B Second flow detection unit 10 Flow path 11 Flow wall 20 Pressure receiving portion 20A Cylindrical portion 20B Slit 21 Inner layer portion 22 Outer layer portion 23 Window portion 30 Pressure detection portion 30A First air chamber (differential pressure chamber)
30B... Second air chamber 32... Cantilever 35... Cavity housing 50... Pressing member 70... Signal processing circuit

Claims (9)

a channel having a flow wall that expands and contracts due to changes in the pressure of the fluid flowing inside;
An inner layer portion that covers at least a portion of the periphery of the flow wall and varies in volume according to expansion and contraction of the flow wall, and an air-impermeable outer layer portion that surrounds the inner layer portion. a pressure-receiving portion provided with a window through which the gas in the inner layer enters and exits as the volume of the inner layer changes;
and a pressure detection unit having a cantilever that is flexurally deformed by the gas entering and exiting through the window. 2. The flow detection device according to claim 1, wherein the inner layer portion is formed of an elastic body having communicating cells. 3. The flow detector according to claim 2, wherein said elastic body is polyurethane foam. The flow detection device according to any one of claims 1 to 3, wherein the inner layer portion is softer than the flow wall. The flow detection device according to any one of claims 1 to 4, wherein the pressure detection unit includes a cavity housing that forms a differential pressure chamber that communicates with the window with the cantilever interposed therebetween. . The flow detection device according to any one of claims 1 to 5, further comprising a pressing member that presses the pressure receiving portion against the flow wall. The pressure receiving portion includes a cylindrical portion surrounding the flow wall,
The flow detection device according to any one of claims 1 to 6, wherein a slit extending in the longitudinal direction of the flow path is formed in the tubular portion. The flow detection device according to any one of claims 1 to 7, wherein the flow wall is surrounded by a plurality of flow detection units including the pressure receiving section and the pressure detection section. The plurality of flow detection units includes a first flow detection unit and a second flow detection unit facing each other across the flow path,
8. A signal processing circuit that adds the signals output from the pressure detection sections of the first flow detection unit and the second flow detection unit to cancel vibration noise of the flow path. The flow detection device according to .

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